1. Field of the Invention
The present invention relates to a curing epoxy resin composition which permits water-repellent and ink (recording solution)-repellent surface treatment, and a method of treating a surface of a substrate by using the resin composition. Particularly, the present invention relates to an epoxy resin composition capable of forming a film pattern by irradiation with an active energy ray such as ultraviolet irradiation or the like, a method of treating a surface of a substrate by using the resin composition, an ink jet recording head subjected to ink-repellent treatment, and an ink jet recording apparatus using the ink jet recording head.
2. Description of the Related Art
In various fields, a method of applying a water-repellent coating to a member required to have water resistance and ink repellency to obtain these properties is generally known, and resin materials and coating materials used for the method have been developed.
For example, fluoropolyolefin and a fluororesin coating material having perfluoro groups are thermally and chemically stable, excellent in weather resistance, water resistance, solvent resistance, etc., and further excellent in release property, abrasion resistance and water repellency, and widely used for various applications.
For example, in an ink jet-system recording head in which an ink is discharged as droplets from a discharge orifice and adhered to paper or the like to record or form an image, the discharge orifice preferably has the following characteristics:
(1) Residual ink of ink columns having turned into droplets is immediately held back into a nozzle.
(2) Ink droplets adhering to a nozzle surface can be readily wiped off by a cleaning operation.
(3) The nozzle surface has excellent scratch resistance against the cleaning operation and paper transfer.
(4) In repeated formation of droplets and ink refilling, a meniscus is formed on the nozzle surface.
(5) The discharge direction is a normal to the meniscus.
(6) Even with an ink having low surface tension, or under low-negative pressure, a boundary tension, i.e., a contact angle, sufficient to form the meniscus is obtained.
These characteristics are desirable because they are directly concerned with improving printing performance of an ink jet recording head in which an ink adhering to the periphery of the orifice causes a deviation in the discharge (flying) direction of the ink droplets discharged from the orifice, thereby failing to perform printing with high precision. In order to prevent adhesion of the ink to the vicinity of the discharge orifice, which causes a deviation in the discharge direction, a method is known, in which the surface of the discharge orifice is subjected to water-repellent treatment.
The requirement for the performance of a water-repellent film has been significantly increased in response to recent rapid improvements in performance of ink jet printers. Namely, in an ink jet head, the water-repellent film is also required to have a high degree of fine processability (for example, excellent optical processability, or the like) with refinement of a nozzle and development of a multi-nozzle. Also, the water-repellent film must have basic characteristics such as adhesion to a substrate and ink resistance. For example, water repellency and adhesion are less affected by contact with an ink. In order to improve the performance of the ink itself, various attempts are made to improve the ink by using a polar organic solvent, adjusting the ink to a high pH value, and the like. In order to prevent the water repellency and adhesion to the substrate from deteriorating due to contact with the ink, the water-repellent film is required to have good ink resistance, for example, alkali resistance and hydrolysis resistance. It is difficult to develop a material satisfying these requirements and having a high degree of fine processability.
As a result of various investigations for solving the above problem, the inventors have found an epoxy resin composition having high resolution (excellent fine optical processability) and suitable for forming a water-repellent and ink-repellent cured film having a high contrast (excellent edge sharpness in optical processability).
Accordingly, an object of the present invention is to provide an epoxy resin composition capable of forming a cured film having excellent water-repellency, ink-repellency and ink resistance and high adhesion to a substrate, and capable of fine processing.
Another object of the present invention is to provide a method of treating a surface of a substrate capable of water-repellent treatment with high quality, durability and precision while selecting a treatment position,
A further object of the present invention is to provide an ink jet recording head capable of stably discharging ink, and an ink jet recording apparatus comprising the ink jet recording head.
In order to achieve these objects, in an aspect of the present invention, an epoxy resin composition comprises the following:
(A) An alkylsiloxane-containing epoxy resin having at least a monomer unit represented by the structural formula (a) below and a monomer unit represented by the structural formula (b) below, and at least two each of alkyl siloxane groups and alicyclic epoxy groups in its molecule.
(B) A cationic polymerization catalyst.
(C) A polyfunctional epoxy compound serving as a compatibilizer or reaction accelerator, and having a molecular weight of 300 or more, and a static viscosity at 25xc2x0 C. of 1,000 cps or more. 
In another aspect of the present invention, a method of selectively treating a surface of a substrate comprises the following steps:
(i) The step of coating a coating solution containing the epoxy resin composition on a substrate and then drying the resultant coating to form a film;
(ii) The step of irradiating the film with an active energy ray through a mask to form a pattern; and
(iii) The step of dissolving a portion of the film, which is not irradiated with the active energy ray, in a liquid capable of dissolving the composition.
In still another aspect of the present invention, a method of selectively treating a substrate surface comprises the following steps:
(i) The step of coating a coating solution containing the epoxy resin composition on a substrate and then drying the resultant coating to form a film;
(ii) The step of irradiating the film formed in the previous step with heat or an active energy ray to cure the film; and
(iii) The step of selectively removing the film cured in the step (ii).
In a further aspect of the present invention, an ink jet recording head comprising a discharge orifice for discharging an ink, wherein at least the periphery of the discharge orifice is coated with a cured film of the epoxy resin composition, is provided.
In a still further aspect of the present invention, an ink jet recording apparatus comprising the above-described ink jet recording head is provided.
Further objects, features and advantages of the present invention will become apparent from the following description of the preferred embodiments with reference to the attached drawings.